a) Light curve of the object (top panel) and of a reference star (bottom) observed with the NTT. The object magnitudes were corrected using the variations of the reference stars. The night was not perfectly photometric, so a zero point from another night was used. The reference star magnitudes are not corrected for extinction and are shown to illustrate that the extinction did not vary by much. b) Light curve of the object observed with TRAPPIST.